Why does life thrive on earth

How did life begin and evolve on Earth, and has it evolved elsewhere in the Solar System? Outer Solar System. Small Bodies of the Solar System. Helpful Links Science-funded Nuggets. Gravity Assist Podcast. Planetary Defense Coordination Office. Planetary Science Mission Posters. Cyanobacteria, and bacteria in general, are prokaryotic life forms. This characteristic is distinctive of bacteria and archaea; all other life forms on Earth, including real algae, consist of eukaryotic cells with organelles and with genetic material contained in one place the nucleus.

Bacteria and archaea are hardy creatures. They thrive in hot, cold, salty, acidic and alkaline environments in which most eukaryotes would perish.

Despite this, they have a bad image: after all, bacteria cause many diseases in humans. Yet without them we may not be here at all. Cyanobacteria then went a step further: they started to utilise water during photosynthesis, releasing oxygen as a by-product. But we may owe bacteria more than the air we breathe. It is likely that eukaryotic cells, of which humans are made, evolved from bacteria about two billion years ago.

Some stars only live a few million years before dying. Still, "life might originate very fast, so age is not that important," astrobiologist Jim Kasting at Pennsylvania State University told OurAmazingPlanet.

For instance, the Earth is about 4. The oldest known organism first appeared on Earth about 3. However, more complex forms of life did take longer to evolve — the first multicellular animals did not appear on Earth until about million years ago. Because our sun is so long-lived, comparatively, higher orders of life, including humans, had time to evolve.

Other researchers have suggested that plate tectonics is vital for a world to host life — that is, a planet whose shell is broken up into plates that constantly move around.

For instance, carbon dioxide helps trap heat from the sun to keep Earth warm. This gas normally gets bound up in rocks over time, meaning the planet would eventually freeze. Plate tectonics helps ensure this rock gets dragged downward, where it melts, and this molten rock eventually releases this carbon dioxide gas back into the atmosphere through volcanoes.

Seager agreed, saying that "volcanism might very well provide enough fresh supplies of whatever life might need. Other factors researchers have trotted out for why life succeeded on Earth include how little variation there is in our sun's radiation compared with more volatile stars, or how our planet has a magnetic field that protects us from any storms of charged particles from the sun.

Violent bursts of radiation could have scoured life from Earth in its early, fragile stages. Still, "people are constantly rethinking each of these things and how important they are," Seager said.